Cultural and linguistic adaption and testing of the Health Literacy Questionnaire (HLQ) among healthy people in Korea

Backgrounds This study administered the Health Literacy Questionnaire (HLQ) among Korean adults to examine its factor structure, reliability, and validity. Methods The HLQ items were translated and culturally adapted to the Korean context. The convenience sampling method was used, and data were collected. The difficulty level, confirmatory factor analysis (CFA) using diagonal weighted least squares (DWLS) estimator in R, discriminant validity, and composite reliability were performed. Results The easiest scale to obtain a high score was “Scale 4. Social support for health” and the hardest was “Scale 7. Navigating the healthcare system.” Nine one-factor models fitted well. The nine-factor structural equation model fitted the data well. All HLQ scales were homogenous, with composite reliability. Conclusions The Korean version of the HLQ has a strong construct and high composite reliability when applied to Korean adults.


Introduction
Health literacy refers to the ability to understand health information that is essential to managing diseases, promoting health, and engaging in action. It encompasses comprehension of various medical information, including diet, exercise, prescriptions, and medication instructions. According to the US National Institute of Health, health literacy is the "degree to which The participants were randomly recruited online via "Google 1 Forms" by announcing recruitment on a hospital bulletin board for participants who met the inclusion criteria in the metropolitan area. The inclusion criteria were (a) adults 19 years and over and (b) ability to speak and understand Korean. Confirmatory factor analysis (CFA) requires a minimum of 300 participants [24]; we enrolled 450 participants due to potential dropouts. A total of 450 people participated in the survey, and after excluding 31 who dropped out during the survey, 419 people were included in the final analysis.

Instruments
The Health Literacy Questionnaire. The HLQ comprises 44 items representing nine independent health literacy scales [15]. The nine scales are 1. Feeling understood and supported by healthcare providers (4 items), 2. Having sufficient information to manage my health (4 items), 3. Actively managing my health (5 items), 4. Social support for health (5 items), 5. Appraisal of health information (5 items), 6. Ability to actively engage with healthcare providers (5 items), 7. Navigating the healthcare system (6 items), 8. Ability to find good health information (5 items), 9. Understand health information well enough to know what to do (5 items). Scales 1-5 (Part 1) are scored using response options indicating the level of agreement (ranging from 1 = strongly disagree to 4 = strongly agree). Scales 6-9 (Part 2) are scored using response options indicating difficulty (from 1 = cannot do or usually difficult to 5 = very easy). The results are nine scale scores, which were calculated as the average of the item scores of each scale, with higher scores indicating potential health literacy strengths.

Translation of the Health Literacy Questionnaire (HLQ)
Following consultation with the original authors of the HLQ, a license to adapt the HLQ was obtained (#TL1806IA 12/1/2018). Translation and back-translation were performed in accordance with the Swinburne Translation Integrity Procedure [25]. This is a systematic translation method that uses item intents (descriptions of the meanings of items) to support forward translators to choose words and phrases that maximize measurement equivalence across languages and also considers linguistic and cultural appropriateness [25,26]. In step one, two Korean native translators independently translated the English version into Korean (forward translation). In step two, a third Korean native reviewed the two translations to choose the best one, combine the two, or propose another translation (Consensus forward translation). In step three, one bilingual translator fluent in Korean and English back-translated the Korean-translated version into English (Back-translation). The bilingual translator had expert knowledge in medicine and public health and did not participate in the translations in steps one and two. In step four, the questionnaire developer, the Korean translation team, and two bilinguals conducted a quality assurance consensus meeting via teleconference. During this meeting, each translated item was reviewed to assess cultural appropriateness and measurement invariance. Most of the forward translations were accepted during the consensus discussion. However, some items were revised through discussion to better reflect the intended meaning of the item. For example, "I feel I have good information about. . ." (Scale 2) was revised to "I feel there is good information available to me about. . ." In step five, the completed translation was edited for accurate grammar and spelling to finalize the Korean version of the HLQ.

Data collection
The Institutional Review Board of Ajou University Hospital (AJIRB-SBR-SUR-21-117), the authors' affiliated university hospital, reviewed and approved research procedures. Thereafter, data were collected through Google 1 Forms from April 28 to September 11, 2021. The survey link was published on a medical center dashboard. Information about the study was also posted on institutional homepages for recruitment. The study announcement described the study's purpose, method, and selection criteria. We provided a Quick Response code to access detailed information regarding the study and survey. Potential participants accessed the survey link using the Quick Response code once they agreed to participate. Due to the nature of the online survey, voluntary participation was considered as consent to enroll in the study. Study participants received mobile gift cards ($5) after they completed the survey. A detailed explanation of the research was provided in a separate explanatory note, including a clause that there would be no disadvantages due to participation or non-participation in the research. The survey took approximately 15 minutes to complete. The study was conducted according to the Declaration of Helsinki principles. A formal informed consent was waived due to the nature of the online survey.

Statistical analysis
IBM SPSS Statistics 26.0, R 4.1.2 software was used to analyze data. Descriptive statistics was used to analyze participants' demographic characteristics. The mean score, response range of each item, and the estimated difficulty of the nine scales were analyzed. The HLQ was completed in two ways. Therefore the difficulty was also assessed using two methods. First, Part 1 (Scales 1-5) was rated as agree/disagree. The difficulty was determined based on the percentage of "strongly disagree" or "disagree" against "agree" or "strongly agree." Thereafter, Part 2 (Scales 6-9) was rated based on the percentage of "cannot do or always difficult," "usually difficult," and "sometimes difficult" against "usually easy" and "always easy" [15].
The construct validity of the HLQ has been established in various languages [15,19,27]; therefore, the construct validity of the Korean version of the HLQ was evaluated using CFA. The items of the HLQ were rated on four and five-point ordinal responses. Thus, ordinal variables were analyzed with diagonal weighted least squares (DWLS) [28]. The latent variable analysis package of the R software was used [29]. First, a one-factor CFA model was conducted to determine whether the data for each factor fitted the model. The standardized and non-standardized factor loadings, R 2 (variance of observed variable explained by latent variables), standard error, and 95% confidence interval (CI) of the observed variables were analyzed. Onefactor CFA model fit was tested using chi-square, Comparative Fit Index (CFI), Tucker-Lewis Index (TLI), Root Mean Square Error of Approximation (RMSEA), and the Standard Root Mean Square Residual (SRMR). A CFI > 0.95, TLI > 0.95, SRMR< 0.08 and RMSEA< 0.06 indicated a close fit, and 0.06 < RMSEA< 0.08 indicated a reasonable fit. Thereafter, a strict nine-factor CFA model without correlated residuals or cross-loadings was fitted to the data. Discriminant validity was assessed by analyzing inter-factor correlations with Spearman rank correlation, and a correlation coefficient of 0.8 or higher indicated a low discriminant validity.
Reliability was evaluated using Cronbach's α and composite reliability (CR) for internal consistency [30]. Cronbach's α is a biased estimate of reliability for consistency; items are correlated or loaded onto the same factor [31]. Thus, CR provides an unbiased reliability estimate of the study population [15,30]. In this study, we calculated both Cronbach's α and CR with reference to the literature [15,18,19,27]. A CR of .70 or higher and .95 or lower was deemed desirable [32].

Sociodemographic characteristics of participants
The sociodemographic characteristics of participants are shown in Table 1. The total participants consisted of 68.7% women from 20 to 82 years, with a mean age of 48.8 years (SD = 13.7). Approximately 7.2% of the participants had under middle school level education, which is compulsory education in Korea. Over 70% of participants reported high economic levels, and less than 10% lived alone. Approximately 50% of the participants were diagnosed with at least one chronic disease, such as hypertension, diabetes, or arthritis, and were receiving treatment, and 71.8% reported high interest in their health ( Table 1).

The difficulty level of the Korean version of the HLQ
The level of difficulty of the Korean version of the HLQ ranged from 11.6-46.7% for Part 1. Scale 4. Social support for health was the least difficult (11.6%); however, Scale 2. Having sufficient information to manage my health was the most difficult (46.7%). The difficulty of Part 2 ranged from 53.1-55.7% and was higher than that for Part 1. Scale 8. Ability to find good health information was the least difficult (53.1%), and Scale 7. Navigating the healthcare system was the most difficult (55.7%) ( Table 2).
On the one hand, by items (44 items), "Discuss things with healthcare providers until you understand. . ." (Scale 6), "Decide which healthcare provider you need to see. . ." (Scale 7), "Work out what the best care is for you" (Scale 7), and "Read and understand all the information on medication labels" (Scale 9) were perceived as difficult (� 60%). On the other hand, "I have at least one person who can come to medical," "When I feel ill, the people around me really understand," and "I have strong support from family or friends" on Scale 4 were perceived as easy (� 10%) ( Table 2). Table 2 shows the results of CFA performed to evaluate the construct validity of the HLQ. First, the fit of the nine one-factor CFA models was analyzed. Except for Scale 5 (CFI = 0.967, TLI = 0.935, SMSR = 0.061), the CFI and TLI were 0.95 or higher, and SMSR were below 0.08   Second, the fitness of a full nine-factor CFA model without correlated residuals or crossloadings was analyzed, and the fit indices met the cutoffs (χ 2 DWLS (df = 866) = 1993.353, p < 0.001, CFI = 0.975, TLI = 0.973, SRMR = 0.054, RMSEA = 0.056). Factor loading was satisfactory or better, at � 0.60 (0.700-0.953) for 43 out of 44 items. The factor loading of the remaining item ("I have at least one person who can come to medical. . .") was 0.570, and close to a satisfactory level.

Psychometric properties of the Korean version of the HLQ
Discriminant validity was determined by analyzing the inter-factor correlations among the nine scales (Table 3). The inter-factor correlations ranged from 0.373 (scales 3 and 4) to 0.897 (scales 6 and 7). Of 36 correlations, six were � 0.80. The correlations ranged from 0.373-0.657 in Part 1 and 0.809-0.897 in Part 2 of HLQ. A high inter-factor correlation (� 0.80) suggests a potentially poor discriminant validity of the HLQ.
The CR scores of all nine scales of the HLQ were high at 0.8 or higher. The CR was the highest for Scale 7 (Navigating the healthcare system; 0.933) and lowest for Scale 4 (Social support for health; 0.806) ( Table 2).

Discussion
The HLQ is an instrument enabling a broad assessment of health literacy. It has been translated into multiple languages worldwide, currently including Korean, to measure health  Difficulty level for scales 6-9 was calculated as the proportion responding cannot do, very difficult, or quite difficult as against quite easy and very easy. https://doi.org/10.1371/journal.pone.0271549.t002 literacy in individuals or groups [15]. In the present study, the Korean translation of the HLQ was finalized, and psychometric validity evidence was presented. We applied a rigorous ninefactor confirmatory factor analysis (with no cross-loading or correlated residuals) and found that all items loaded strongly on their hypothesized factor. We also demonstrated that all scales had good to excellent reliability. The Korean version of the HLQ appears to be more difficult for respondents to score higher than the original version [15] (Part 1: 10.0~38.0%, Part 2: 7.0~42.0%). However, the level of difficulty was similar to the Danish (Part 1: 45.8%, Part 2: 50.9%) [17] and French (Part 1: 45.1%, Part 2: 69.1%) [19]. The reason may be pertinent to the differences in the healthcare delivery system and cultural sensitivity in the country where the original instrument was developed. Part 2 was perceived as more difficult (53.1~55.7%) than Part 1 (11.6~46.7%), similar to the French version [19]. Part 1 consisted of questions about the subject's health information search experience and utilization level. Part 2 consisted of questions about how difficult it was for participants to search for and use health information, contributing to the perceived difficulty. Among nine scales in the HLQ, Scale 7 (Navigating the healthcare system; 55.7%) and Scale 6 (Ability to actively engage with healthcare providers; 55.4%) were perceived as the most difficult. This suggests that individuals find "navigating the healthcare system" and "engaging with healthcare providers" challenging. Our study population predominantly comprised healthy individuals who may less frequently consult a healthcare provider about their health than those with a chronic condition. Thus, they may have indicated "cannot do or always difficult" regardless of the appropriateness of the items. Thus, it is necessary to evaluate HLQ levels and perceived difficulties exclusively among individuals with chronic diseases.
We performed CFA to test the construct validity of the HLQ. The one-factor CFA models for nine scales had a close fit overall, confirming unidimensionality. This result is similar to the CFA performed in the Danish [17] and French versions [19]. The factor loading was below 0.6 for between two and 13 items in the other versions of the HLQ, including the Danish [17] and French versions [19]. However, we found all items loaded onto a single factor (� 0.6) in our analysis. Thereafter, we fitted the data to the nine-factor CFA model, and the fit indices met the criteria, thus confirming a good model fit. This study is a better fit than that reported for the Danish [17] and French versions [19]. The Korean HLQ has satisfactory construct validity based on these fit indices and factor loadings. All nine factors of the Korean version of the HLQ had a CR of 0.80 or higher. Similarly, a high CR was reported for the original [15], Danish [17], and French versions [19]. Therefore, HLQ has good reliability. Discriminant validity was evaluated using inter-factor correlations. Scales 1-5 demonstrated good discriminant validity. However, discriminate validity was less clear for Scales 6-9, with the correlation coefficient > 0.80. The English [15] and German versions [18] reported similar results. The construct definitions and the item content indicate that the constructs are measuring different elements of health literacy. However, the high correlations among these scales may be attributed to addressing a common overarching issue related to ability or confidence in finding (Scale 8), understanding (Scale 9), navigating (Scale 7), and engaging (Scale 6). This suggests that there may be a high-order factor present [15], or the factors are causally related [16]. Future studies should investigate this issue in diverse settings among people with a wide range of health literacy strengths and challenges.
The findings of this study indicate that the Korean version of the HLQ is likely to be a useful tool for understanding health literacy in healthy individuals and people with health conditions in Korea. It may also be useful for researching adherence to health education and self-management interventions and exploring determinants of health-related quality of life.
This study has a few limitations. First, adults aged 19 years and older were conveniencesampled in the Seoul Metropolitan area in Korea. More than half of the study participants were highly educated, and the study was conducted in an urban area. Thus, generalizing the results to the general population requires caution, and replication studies on the general population from more diverse communities are needed. Second, we collected data using a QR code; thus, individuals with easy access to electronics and the Internet may have been primarily recruited. Hence, subsequent studies should consider participants' access to health-related information and collect data using various media types. The Korean version of the HLQ was developed through a systematic translation process using forward and carefully guided by detailed item intents to ensure good linkage to the originally-intended constructs developed in Australia. However, the instrument is still vulnerable to systematic errors due to cultural gaps, such as differences in the healthcare delivery systems between the two countries. Therefore, caution should be applied when interpreting results.

Conclusion
Health literacy allows individuals to engage in daily health practices; hence, it is considered essential to meet health needs. Health literacy varies across individuals; therefore, healthcare providers should assess patients' comprehensive health literacy before providing treatment, nursing care, or tests. The present study translated the HLQ into Korean and tested this version in an urban population. The validity and reliability results support the validity of data from the Korean version of the HLQ in the study context. These initial findings, i.e., strong psychometric properties, indicate that the Korea version of the HLQ is a useful tool to generate an in-depth evaluation of patients' experiences, skills, strengths, and needs pertaining to health literacy.